Apparatus and methods for electrochemical hydrogen manipulation

ABSTRACT

Apparatus and methods are provided for electrochemical hydrogen manipulation. In one example, an electrochemical cell is provided utilizing an acid doped polybenzimidazole membrane having a proton conductivity of at least 0.1 S/cm and comprising phosphoric acid in a ratio of at least 20 moles phosphoric acid to polybenzimidazole repeating unit. The polybenzimidazole membrane can be produced by a sol-gel process. Additional concepts are also described.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 USC 119 (e) from U.S.Provisional Application No. 60/763,457, filed Jan. 30, 2006, namingBenicewicz et al. as inventors, and titled APPARATUS AND METHODS FORELECTROCHEMICAL HYDROGEN MANIPULATION.” That application is incorporatedherein by reference in its entirety and for all purposes.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to apparatus, methods and applications forelectrochemical hydrogen manipulation, including the use ofelectrochemical cells to transfer, purify or compress hydrogen from asource gas that contains hydrogen.

BACKGROUND

Hydrogen based energy devices are of increasing interest, due in part toadvantages provided in efficiency and environmental impact overtraditional combustion based technologies.

A variety of electrochemical fuel cell technologies are known, whereinelectrical power is produced by reacting a fuel such as hydrogen in anelectrochemical cell to produce a flow of electrons across the cell,thus providing an electrical current. For example, in fuel cellsutilizing proton exchange membrane technology, a gas containing hydrogenis reacted at an anode side of the fuel cell. Each hydrogen moleculethat is reacted produces two protons which pass through a protonconductive membrane to a cathode side of the fuel cell. The protons atthe cathode react with oxygen to form water, and the residual electronsat the anode travel through a conductive path around the protonconducting membrane from anode to cathode to produce an electricalcurrent. The technology is closely analogous to conventional batterytechnology.

Electrochemical cells can also be used to selectively transfer (or“pump”) hydrogen from one side of the cell to another. For example, in acell utilizing a proton exchange membrane, the membrane is sandwichedbetween a first electrode and a second electrode, a gas containinghydrogen is placed at the first electrode, and an electric potential isplaced between the first and second electrodes, the potential at thefirst electrode with respect to ground (or “zero”) being greater thanthe potential at the second electrode with respect to ground. Eachhydrogen molecule reacted at the first electrode produces two protonswhich pass through the membrane to the second electrode of the cell,where they are rejoined by two electrons to form a hydrogen molecule(sometimes referred to as “evolving hydrogen” at the electrode).

Electrochemical cells used in this manner are sometimes referred to ashydrogen pumps. In addition to providing controlled transfer of hydrogenacross the cell, hydrogen pumps can also by used to separate hydrogenfrom a gas containing other components besides hydrogen. The hydrogenproduction from the cell can also be used to compress the hydrogen gasas it is evolved.

There is a continuing need for apparatus, methods and applications forelectrochemical hydrogen manipulation, including the use ofelectrochemical cells to transfer, purify or compress hydrogen.

SUMMARY OF THE INVENTION

Apparatus, methods and applications are provided for electrochemicalhydrogen manipulation. In one aspect, an electrochemical cell isprovided utilizing an acid doped polybenzimidazole (PBI) membrane havinga proton conductivity of at least 0.1 S/cm and comprising phosphoricacid (PA) in a ratio of at least 20 moles phosphoric acid to PBIrepeating unit. As an example, the PBI membrane can be produced by asol-gel process. In some embodiments, such systems can be operatedutilizing hydrogen that is dry or otherwise un-humidified or less thansaturated with water.

In another aspect, an electrochemical cell is provided that includes apolymeric layer that abuts an external surface of an acid doped PBImembrane. As examples, the polymeric layer can be a polymeric acidlayer, e.g., polyvinyl phosphonic acid or a polyvinyl sulfonic acid.Other materials are also possible.

In another aspect, an electrochemical cell is provided that includes anacid doped PBI membrane associated with a porous support layer. Asexamples, the support layer can be encapsulated within the membrane, orcan be provided along an external surface of the membrane. As anexample, the support layer can be expanded polytetrafluoroethylene.Other materials are also possible.

In another aspect, apparatus and methods are provided wherein anelectrochemical cell is used to provide hydrogen to an inlet of amechanical compressor. In other embodiments, a mechanical compressor canbe adapted to provide compressed hydrogen to an inlet of anelectrochemical cell.

In another aspect, a method is provided for operating an electrochemicalcell utilizing an acid doped PBI membrane and non-graphitic carbon basedcomponents such as flow field plates, etc. An electric potential isapplied between first and second electrodes of the cell, and thepotential is maintained below 0.8 volts.

In another aspect, a method is provided for utilizing an electrochemicalcell to meter a flow of hydrogen. As an example, an electricalmeasurement can be taken from an electrochemical cell operating in ahydrogen pumping mode to correlate an amount of hydrogen transferredacross the cell. The correlated hydrogen flow can be compared to athreshold value to allow the cell to be shut off when a desired amountof hydrogen has been transferred.

Other aspects and features of the invention will be apparent from thefollowing Detailed Description and from the claims.

DETAILED DESCRIPTION OF THE INVENTION

It will be appreciated that the apparatus, methods, and applications ofthe invention can include any of the features described herein, eitheralone or in combination.

One aspect of the invention is a method of operating an electrochemicalcell, including at least the following steps: applying an electricpotential between a first electrode and a second electrode of anelectrochemical cell, wherein the first electrode has a higher electricpotential with respect to zero than the second electrode, wherein thefirst and second electrodes have an acid doped PBI membrane betweenthem, the membrane having a proton conductivity of at least 0.1 S/cm;and flowing a hydrogen gas across the first electrode and evolvinghydrogen at the second electrode. As discussed above, each hydrogenmolecule reacted at the first electrode produces two protons which passthrough the membrane to the second electrode of the cell, where they arerejoined by two electrons to form a hydrogen molecule. In the presentinvention, the hydrogen gas can be pure hydrogen, or any gas containingany amount of hydrogen, for example containing various impurities. Thehydrogen gas may also be referred to synonymously as a source gas,hydrogen source gas, hydrogen containing gas, etc.

The direction of hydrogen “pumping” across the membrane can becontrolled according to the polarity of the electrical potential betweenthe first and second electrodes. The hydrogen flows between theelectrodes from higher to lower potential with respect to ground orzero. Thus, reversing the polarity across the cell can reverse thedirection of hydrogen flow between the electrodes. Methods under thepresent invention may thus include the step of reversing a polarity ofthe electric potential between the first electrode and second electrodeto reverse a direction of hydrogen flow through the cell. In thiscontext, “reversing a direction” is taken to mean selectively evolvinghydrogen at either electrode according to the polarity of the potential(in addition to actually reversing an active flow of hydrogen throughthe cell).

In another embodiment, instead of a potential being placed across thefirst and second electrodes, an electrical load can be placed acrossthem, and as a result, hydrogen will be “pumped” from the side of themembrane having the higher partial pressure of hydrogen to the sidehaving the lower partial pressure of hydrogen. Methods under the presentinvention may thus include the step of removing the electric potentialbetween the first electrode and the second electrode, and connecting anelectric load between the first electrode and the second electrode.

It will be appreciated that PBIs are a class of heterocyclic polymers.Various examples of PBI polymers are provided in the teachings of U.S.Pat. No. 4,814,399, which is hereby incorporated by reference. Asdiscussed, for example, in the above referenced patent, PBI membranesused in electrochemical cells are normally imbibed with an ionconductive material such as phosphoric acid (PA). PBI membranes that areassociated with PA through soaking, imbibing, through the sol-gelprocess discussed below, or by any other process are sometimes referredto as acid doped PBI membranes.

PBI membranes used with the present invention can be prepared by asol-gel process, as described in the article, High-TemperaturePolybenzimidazole Fuel Cell Membranes Via A Sol-Gel Process, Chem.Mater. Vol. 17, No. 21, 2005, which is incorporated by reference andexcerpted below. It is noted that one inventor of the present case is anauthor of this article.

Under the sol-gel process, polymerization to produce PBI polymers can becarried out using polyphosphoric acid (PPA) as both the polycondensationagent and the polymerization solvent starting from tetraaminobiphenyl(TAB) and dicarboxylic acid. After polymerization, the PBI solution inPPA can be directly cast at approximately 200 to 220 C without isolationor redissolution of the polymers. Upon casting, hydrolysis of the PPA toPA induces a sol-gel transition that produces membranes with higherratios of PA to PBI repeating unit than currently believed possible withother PBI membrane production techniques. For example, PBI membranesproduced under the sol-gel process can have more than 20 moles of PA perPBI repeating unit (e.g., 20-40 moles of PA per PBI repeating unit). Themain example discussed in the article referenced above had approximately32 moles of PA per PBI repeating unit. It will be appreciated that overtime, and particularly during operation of an electrochemical cellcontaining a PBI membrane, some PA may migrate from the membrane overtime.

Without wishing to be bound by theory, it is believed that the higher PAloading in PBI membranes produced under the sol-gel process results ingreater proton conductivity. As examples, such membranes generally haveconductivities of at least 0.1 S/cm, or even at least 0.2 S/cm.

The following description of PBI membrane preparation under the sol-gelprocess is taken from the article referenced above.

Materials and PBI Synthesis. Isophthalic acid and terephthalic acid werepurchased from Amoco (99+% pure) and dried prior to use.3,3′,4,4′-Tetraaminobiphenyl (TAB, polymer grade) was donated byCelanese Ventures, GmbH and used as received. Polyphosphoric acid (115%)was used as supplied from Aldrich Chemical Co. and FMC Corporation. Thegeneral procedure for the synthesis of polybenzimidazoles (PBIs) isdescribed as follows: Isophthalic acid (12.460 g, 75 mmol) and TAB(16.074 g, 75 mmol) were added to a three-neck resin reaction flask in anitrogen atmosphere glovebox, followed by 200 to 600 g of polyphosphoricacid. The reaction mixture was stirred using a mechanical overheadstirrer and purged with a slow stream of nitrogen, and the reactiontemperature was controlled by a programmable temperature controller withramp and soak features. The typical polymerization temperatures wereapproximately 190-220 C for 16 to 24 h. During the polymerization, thereaction mixture became more viscous and developed a dark brown color. Asmall amount of the reaction mixture was poured into water and isolatedas a brown mass. The mass was pulverized, neutralized with ammoniumhydroxide, washed thoroughly with water, and dried in a vacuum oven for24 h at 100 C to obtain the PBIs for further characterization.

Membrane Preparation. The membranes were prepared by casting thepolymerization solution directly onto untreated glass substrates in airusing a film applicator with a gate thickness ranging from 0.127 mm (5mils) to 0.635 mm (25 mils) and allowed to cool from polymerizationtemperature (190 to 220 C) to room temperature in a few minutes.Hydrolysis was allowed to proceed under controlled conditions (forexample, by exposing films for 24 h at 25 C and a relative humidity of40±5%). Since both PBI polymer and polyphosphoric acid are extremelyhygroscopic, moisture was absorbed from the atmosphere and hydrolyzedthe polyphosphoric acid solvent to phosphoric acid. Some drain-off ofwater and phosphoric acid was then observed during the hydrolysisprocess which caused a shrinkage of membrane dimensions of 10 to 20%.The amount of water absorbed did not correlate directly with themembrane PA-doping level.

Characterization Methods. The phosphorus nuclear magnetic resonancespectra (31P NMR) were recorded on a Chemagnetics CMX-360 instrumentoperating at a frequency of 145.71 MHz using 85% PA as externalreference. Polymer films were cast onto thin glass strips and assembledinto an open-ended glass NMR tube with 7.0 mm diameter. The film stripswere then hydrolyzed in an environmental chamber and taken outperiodically for 31P NMR measurements. The membrane acid-doping levelswere determined by titrating a preweighed piece of membrane sample withstandardized sodium hydroxide solution with a Metrohm 716 DMS Titrinotitrator. The samples were then washed with water and dried in a vacuumoven at 100 C for 4 h to obtain the dry weight of polymer. Theacid-doping levels, X, expressed as moles of phosphoric acid per mole ofPBI repeat unit (XH3PO4·PBI) were calculated from the equation:acid-doping level X=(VNaOH CNaOH)/(Wdry/Mw);

where VNaOH and CNaOH are the volume and the molar concentration of thesodium hydroxide titer, while Wdry is the dry polymer weight and Mw isthe molecular weight of the polymer repeat unit, respectively.

Ionic conductivities were measured by a four-probe ac impedance methodusing a Zahner IM6e spectrometer over a frequency range from 1 Hz to 100kHz. A rectangular piece of membrane (3.5 cm×7.0 cm) and four platinumwire current collectors were set in a glass cell. Two outer electrodes6.0 cm apart supply current to the cell, while the two inner electrodes2.0 cm apart on opposite sides of the membrane measure the potentialdrop. The four-probe technique offers many advantages over the two-probetechniques, including measuring the bulk property of the membraneinstead of the surface property and minimizing the error stemming fromcontact resistance and electrode resistance. The cell was placed in aprogrammable oven to measure the temperature dependence of the protonconductivity. The membranes were dried by first heating from roomtemperature to 200 C and holding at 200 C for 1 h. The membrane sampleswere then cooled in a vacuum oven and taken out just before conductivitymeasurement in an effort to keep the samples dry. The conductivities ofthe membrane samples were measured from 20 to 160 C at intervals of 20C. Before the measurements at each temperature set point, the sampleswere held at constant temperature for at least 10 min. Repeatedconductivity measurements showed that reproducible results were obtainedusing this temperature profile and testing procedure. A two-componentmodel with an ohmic resistance in parallel with a capacitor was employedto fit the experimental curve of the membrane resistance across thefrequency range (the Nyquist plot). The conductivities of the membraneat different temperatures were calculated from the membrane resistanceobtained from the ohmic resistance of the model simulation. Protonconductivity was then calculated from the following equation:•=D/(LBR);

where D is the distance between the two current electrodes 2.0 cm apart,L and B are the thickness and width, respectively, and R is theresistance value measured.

One advantage of the electrochemical cells, systems and related methodsprovided under the invention is that they can generally be operatedwithout having to humidify the gas from which hydrogen is removed. It isbelieved that electrochemical cells utilizing PBI membranes produced bytraditional non-sol-gel processes, and other non-PBI fuel cells allrequire that the hydrogen source gas be humidified prior to hydrogentransfer. It is believed that utilization of subsaturated hydrogensource gas will result in an immediate and progressive performancedegradation. The sol-gel PBI based systems under the invention do notexhibit such degradation. Without wishing to be bound by theory, it isbelieved that the higher ratio of PA to PBI repeating unit enables thisaspect of performance. Thus, in some embodiments, the apparatus andmethods provided include the distinction that the hydrogen source gas isunhumidified. In this context, unhumidified means that the gas is lessthan saturated with water, and no step has been taken to increase thesaturation level of the gas. In some embodiments, the hydrogen sourcegas can be dry.

Some embodiments also provide the advantage that they can be used totransfer hydrogen from gasses containing carbon monoxide, includingconcentrated amounts of carbon monoxide that would be sufficient tointerfere with the operation of other polymer electrolyte membraneelectrochemical cells. Without wishing to be bound by theory, it isbelieved that the capability of PBI based membranes to be operated atrelatively high temperatures enables this aspect of performance (e.g.,operating temperatures from 100-200 C, over 140 C, etc.).

In another aspect of the invention, the electrochemical cell can includea polymeric film or layer abutting an external surface of the membrane.For example, the hydrogen source side of the membrane may have such alayer between the membrane and the electrode. Similarly, such a layermay also be placed between the hydrogen evolution side of the membraneand the electrode. Without wishing to be bound by theory, it is believedthat such polymeric layers may assist long term retention of PA in thePBI membrane, particularly in the case of sol-gel PBI membranes havinghigh ratios of PA to PBI repeating unit. As examples, the polymeric filmcan be a polymeric acid layer comprising polyvinyl phosphonic acids,polyvinyl sulfonic acids or other materials suitable for promotingproton transfer. Those of skill in the art will appreciate that othersuitable materials can also be used. In some embodiments, the polymericacid layer can be cross-linked onto the PBI membrane.

In another aspect of the invention, the electrochemical cell can includea porous support layer. For example, in some embodiments, the PBImembrane may have such a layer at its core. In other embodiments, thePBI membrane may have such a layer on the hydrogen source side, or thehydrogen evolution side, or both sides. In one example, the supportlayer can be a porous polymer film such as expandedpolytetrafluoroethylene that is drawn through a sol-gel mixture of PAand PBI, such that the PBI is cast onto the support layer. In anotherexample, the support layer can be a rigid layer such as a ceramicmaterial. It will be appreciated that additional support layercompositions will be suitable. In addition to providing mechanicalsupport, the support layer can also provides additional PA associatedwith the membrane (e.g., support layer with pores containing PA), thusimproving performance and longevity. Where a support layer is placedacross an external surface of the membrane, the support layer willgenerally need to be electrically conductive.

In another aspect, an electrochemical cell can be combined with amechanical compressor adapted to receive an exhaust from the cell. Insome mechanical compressors, the initial stages of compression can beless efficient, and therefore providing initial compression from anelectrochemical cell can improve the efficiency of a combinedcompression system.

A related method of operating an electrochemical cell is provided,including at least the following steps: applying an electric potentialbetween a first electrode and a second electrode of an electrochemicalcell, wherein the first electrode has a higher electric potential withrespect to zero than the second electrode, wherein the first and secondelectrodes have an acid doped polybenzimidazole membrane between them,the membrane having a proton conductivity of at least 0.1 S/cm; flowinga hydrogen gas across the first electrode and evolving hydrogen at thesecond electrode, wherein the hydrogen gas comprises hydrogen; andexhausting hydrogen from the second electrode to an inlet of amechanical compressor.

Conversely, in some cases it may be desirable to minimize the pressuredrop across an electrochemical cell used in a hydrogen pumping mode, orotherwise provide gas to the cell at elevated pressure. Therefore, acombined system is also provided wherein a mechanical compressor isadapted to supply a compressed source gas to an inlet of anelectrochemical cell, wherein the source gas comprises hydrogen, andwherein the electrochemical cell is adapted to transfer hydrogen fromthe compressed source gas to an outlet of the electrochemical cell.

In another aspect, the invention provides a means for utilizing PBIbased electrochemical cells with non-graphitic carbon based components.Operation of such systems has been problematic in the past because therelatively high cell voltages associated with traditional fuel cells(e.g., over 0.8 volt) have resulted in corrosion of the cell, requiringthe use of expensive graphitic materials. However, under the presentinvention, in systems utilizing sol-gel based PBI membranes, it has beenfound that the cells can be operated at substantially lower voltageswhere corrosion will not occur (e.g., under 0.8 volts, under 0.6 volts,or even under 0.3 volts).

The invention therefore provides a related method of operating anelectrochemical cell, including at least the following steps: applyingan electric potential between a first electrode and a second electrodeof an electrochemical cell, wherein the first electrode has a higherelectric potential with respect to zero than the second electrode,wherein the first and second electrodes have an acid dopedpolybenzimidazole membrane between them, wherein the first and secondelectrodes each comprise non-graphitic carbon based components; flowinga gas comprising hydrogen across the first electrode; and maintainingthe electric potential between the first and second electrodes below 0.8volts.

In another aspect, the invention provides a method of metering a flow ofa hydrogen, including at least the following steps: applying an electricpotential between first and second electrodes of an electrochemicalcell; providing gas comprising hydrogen to the first electrode; andremoving the electric potential when a desired amount of hydrogen hasbeen transferred to the second electrode.

This method may also include additional steps including the following:taking an electrical measurement from the electrochemical cell;correlating an amount of pumped hydrogen from the electricalmeasurement; comparing the correlated amount of pumped hydrogen to athreshold value; and generating a signal to remove the electricpotential between the first and second electrodes when the correlatedamount of pumped hydrogen is at least as high as the threshold value.

It is well known to those of ordinary skill in the art how electricalinformation from an electrochemical cell in a hydrogen pumping mode canbe used to correlate the amount of hydrogen transferred across the cell.

In addition to the foregoing, such control methods may also be conductedaccording to non-electrical measurements, such as pressure measurements,etc.

As examples, such methods can be used to accurately control the flow ofhydrogen gas into or out of a hydrogen storage vessel, or from onestream containing hydrogen to another, etc. Such methods can be used tometer hydrogen flow to propulsion systems, such as fuel cell and otherhydrogen based automotive systems requiring metered hydrogen injection.As an example, rather than getting a bulk flow of hydrogen by opening apressure valve on a tank of hydrogen, by utilizing electrochemicalmetering under the present invention, the amount of hydrogen released orinjected from a source can be controlled with extreme precision, onessentially an atom-by-atom basis.

While most of the concepts described herein involve the use of PBImembranes produced under the sol-gel process, in claims where thespecific nature of the membrane is not specified, any suitable membranemay be used, such as those based on non-sol-gel PBI, Nafion, PEEK, etc.

Discussion in the present case is generally made only with respect tothe particular aspects of electrochemical cell technologies affected bythe concepts described herein. Additional details for suitable designsand operating methods for electrochemical cells are well known in theart. As examples, the teachings of U.S. Pat. Nos. 4,620,914 and6,280,865; and published U.S. patent application Ser. Nos. 10/213,798and 10/478,852 are hereby incorporated by reference.

While the invention has been shown or described in only some of itsforms, it should be apparent to those skilled in the art that it is notso limited, but is susceptible to various changes without departing fromthe scope of the invention.

1. A method of operating an electrochemical cell, comprising: applyingan electric potential between a first electrode and a second electrodeof an electrochemical cell; wherein the first electrode has a higherelectric potential with respect to zero than the second electrode;wherein the first and second electrodes have an acid dopedpolybenzimidazole membrane between them, the membrane having a protonconductivity of at least 0.1 S/cm; and flowing a hydrogen gas across thefirst electrode and evolving hydrogen at the second electrode.
 2. Themethod of claim 1, wherein the membrane comprises phosphoric acid at aratio of at least 20 moles phosphoric acid to polybenzimidazolerepeating unit.
 3. The method of claim 1, wherein the membrane comprisesphosphoric acid at a ratio of at least 32 moles phosphoric acid topolybenzimidazole repeating unit.
 4. The method of claim 1, wherein themembrane comprises phosphoric acid at a ratio of at least 40 molesphosphoric acid to polybenzimidazole repeating unit.
 5. The method ofclaim 1, wherein the membrane is prepared by a sol-gel process.
 6. Themethod of claim 1, wherein the membrane is prepared by a process whereinpolyphosphoric acid is used as a solvent for both polymerization andfilm casting.
 7. The method of claim 1, wherein the membrane has aproton conductivity of at least 0.2 S/cm.
 8. The method of claim 1,wherein the electrochemical cell further comprises a polymeric filmabutting an external surface of the membrane.
 9. The method of claim 1,wherein the electrochemical cell further comprises a polymeric acid filmabutting an external surface of the membrane, wherein the polymeric acidfilm comprises polyvinyl phosphonic acid.
 10. The method of claim 1,wherein the electrochemical cell further comprises a polymeric acid filmabutting an external surface of the membrane, wherein the polymeric acidfilm comprises polyvinyl sulfonic acid.
 11. The method of claim 1,wherein the hydrogen gas is unhumidified.
 12. The method of claim 1,further comprising the step of reversing a polarity of the electricpotential between the first electrode and second electrode to reverse adirection of hydrogen flow through the cell.
 13. The method of claim 1,further comprising the steps of removing the electric potential betweenthe first electrode and the second electrode, and connecting an electricload between the first electrode and the second electrode.
 14. A methodof transferring hydrogen from a source gas, comprising: applying anelectric potential between a first electrode and a second electrode ofan electrochemical cell; wherein the first electrode has a higherelectric potential with respect to zero than the second electrode;wherein the first and second electrodes have an acid dopedpolybenzimidazole membrane between them, wherein the membrane comprisesphosphoric acid at a ratio of at least 20 moles phosphoric acid topolybenzimidazole repeating unit; and flowing a hydrogen gas across thefirst electrode and evolving hydrogen at the second electrode.
 15. Themethod of claim 14, wherein the membrane has a proton conductivity of atleast 0.1 S/cm.
 16. The method of claim 14, wherein the membrane has aproton conductivity of at least 0.2 S/cm.
 17. The method of claim 14,wherein the membrane comprises phosphoric acid at a ratio of at least 32moles phosphoric acid to polybenzimidazole repeating unit.
 18. Themethod of claim 14, wherein the membrane comprises phosphoric acid at aratio of at least 40 moles phosphoric acid to polybenzimidazolerepeating unit.
 19. The method of claim 14, wherein the membrane isprepared by a sol-gel process.
 20. The method of claim 14, wherein themembrane is prepared by a process wherein polyphosphoric acid is used asa solvent for both polymerization and film casting.
 21. The method ofclaim 14, wherein the electrochemical cell further comprises a polymericfilm abutting an external surface of the membrane.
 22. The method ofclaim 14, wherein the electrochemical cell further comprises a polymericacid film abutting an external surface of the membrane, wherein thepolymeric acid film comprises a material from the group consisting ofpolyvinyl phosphonic acid and polyvinyl sulfonic acid.
 23. The method ofclaim 14, wherein the hydrogen gas is unhumidified.
 24. The method ofclaim 14, further comprising the step of reversing a polarity of theelectric potential between the first electrode and second electrode toreverse a direction of hydrogen flow through the cell.
 25. The method ofclaim 14, further comprising the steps of removing the electricpotential between the first electrode and the second electrode, andconnecting an electric load between the first electrode and the secondelectrode.
 26. An electrochemical cell, comprising: a proton conductingelectrolyte membrane; a polymeric layer; wherein the membrane has afirst electrode side; wherein the polymeric acid layer abuts the firstelectode side of the membrane; wherein the membrane comprises acid dopedpolybenzimidazole; and wherein a proton conductivity of the membrane isat least 0.1 S/cm.
 27. The electrochemical cell of claim 26, wherein themembrane comprises phosphoric acid at a ratio of at least 20 molesphosphoric acid to polybenzimidazole repeating unit.
 28. Theelectrochemical cell of claim 26, wherein the membrane has a protonconductivity of at least 0.2 S/cm.
 29. The electrochemical cell of claim26, wherein the polymeric layer comprises a material from the groupconsisting of polyvinyl phosphonic acid and polyvinyl sulfonic acid. 30.The electrochemical cell of claim 26, wherein the polymeric layer iscross-linked to the membrane.
 31. An electrochemical cell, comprising: amembrane assembly; wherein the membrane assembly comprises a poroussupport layer; and wherein the membrane assembly comprises apolybenzimidazole layer abutting an external surface of the supportlayer.
 32. The electrochemical cell of claim 31, wherein a firstpolybenzimidazole layer abuts a first electrode side of the supportlayer, and wherein a second polybenzimidazole layer abuts a secondelectrode side of the support layer.
 33. The electrochemical cell ofclaim 31, wherein a first support layer abuts a first electrode side ofthe polybenzimidazole layer, and wherein a second support layer abuts asecond electrode side of the polybenzimidazole layer.
 34. Theelectrochemical cell of claim 31, wherein the support layer comprisesexpanded polytetrafluoroethylene.
 35. The electrochemical cell of claim31, wherein the support layer comprises pores containing phosphoricacid.
 36. The electrochemical cell of claim 31, further comprising apolymeric layer abutting the polybenzimidazole layer.
 37. Theelectrochemical cell of claim 31, further comprising a polymeric acidlayer abutting the polybenzimidazole layer; wherein the polymeric acidlayer comprises a material from the group consisting of polyvinylphosphonic acid and polyvinyl sulfonic acid.
 38. The electrochemicalcell of claim 31, wherein the polybenzimidazole layer is prepared by asol-gel process.
 39. The electrochemical cell of claim 31, wherein thepolybenzimidazole layer is prepared by a process wherein polyphosphoricacid is used as a solvent for both polymerization and film casting. 40.The electrochemical cell of claim 31, wherein the polybenzimidazolelayer has a proton conductivity of at least 0.1 S/cm.
 41. Theelectrochemical cell of claim 31, wherein the polybenzimidazole layerhas a proton conductivity of at least 0.2 S/cm.
 42. The electrochemicalcell of claim 31, wherein the polybenzimidazole layer comprisesphosphoric acid at a ratio of at least 20 moles phosphoric acid topolybenzimidazole repeating unit.
 43. The electrochemical cell of claim31, wherein the polybenzimidazole layer comprises phosphoric acid at aratio of at least 32 moles phosphoric acid to polybenzimidazolerepeating unit.
 44. The electrochemical cell of claim 31, wherein thepolybenzimidazole layer comprises phosphoric acid at a ratio of at least40 moles phosphoric acid to polybenzimidazole repeating unit.